Economic historian Bruce Caldwell writes that in the mid-20th century, with the ascendance of positivism and Keynesian economics, Mises came to be regarded by many as the "archetypal 'unscientific' economist." In a 1957 review of his bookThe Anti-Capitalistic Mentality, The Economist said of von Mises: "Professor von Mises has a splendid analytical mind and an admirable passion for liberty; but as a student of human nature he is worse than null and as a debater he is of Hyde Park standard." The Economist [That's a very amateur standard.] Conservative commentator Whittaker Chambers published a similarly negative review of that book in the National Review, stating that Mises's thesis that anti-capitalist sentiment was rooted in "envy" epitomized "know-nothing conservatism" at its "know-nothingest."